In general, a modem is a device that both modulates and demodulates signals communicated across a wired or a wireless network, and thus, provides an interface for the communication of data over the network. A variety of different waveforms may be transmitted wirelessly using a number of different digital codes, signal processing methods, frequencies, etc. to achieve communication through noisy and error prone channels. Traditionally, the military has used dedicated radio systems that have a radio for each specific application such as VHF, UHF, and HF. More recently, the military has been pursuing software defined radios that include hardware that can be reprogrammed to process different waveforms.
In the past, very low power, efficient modems were fabricated of dedicated, and thus, non-programmable, hardware in combination with a very low power digital signal processor (DSP). Such hardware implementations are cost-effective and low power, but do not meet the current reprogrammable requirements. Currently, reprogrammable modems are implemented using either a very large field programmable gate array (FPGA) or a custom application specific integrated circuit (ASIC). FPGAs avoid the high initial engineering design costs of ASICs, but lack in performance and in efficiency. In general, modems implemented using FPGAs require in the range of 14-19 watts of power when implementing a modern communications waveform such as orthogonal frequency division multiplexing or turbo coding. This power utilization by the FPGA and the corresponding heat dissipation requirement is unacceptable in battery powered applications and in passively cooled environments. What is needed, therefore, is a programmable modem having much lower power utilization, for example, on the order of 2-3 watts. What is further needed is a programmable modem that can be reconfigured to support different communication technologies and resulting waveforms.